Another way to look at it: Herons may not consciously or instinctively move fish between bodies of water, but maybe their survival at some point happened because they did so. I have read or heard many accounts of herons or other birds that eat fish dropping the fish. If onto dry land, the fish dies. If into a BOW, maybe survives and reproduces. It only takes two sunfish, not even of the same subspecies, to populate a BOW.
The silted in pond I renovated in August 2015 had small GSF in it before renovation, and had gone completely dry in the dry summer of 2012. It has NO connection to any other pond, and has a small watershed of only about two acres, and never spilled over between 2012 and 2015.
